MLT geometry assuming a HERMS system

[RoatanBill]

I'm trying to figure out where the reasonable dividing line is in terms of kettle sizes to be able to do experimental brews of 5G of beer (>5G of mash) and also to get the largest kettles to maximize the upper potential.

Moving liquid through the grain bed efficiently is the goal. It seem logical to me that the more surface area the better (within reason) for a given quantity of mash.

For example, take a 15G and a 20G standard kettle filled with a typical grist to water ratio for an average 5G of consumable beer. This is using the kettles at their minimum reasonable capacity. Admittedly, 15G is already too large for this.

The mash will be much shallower in the 20G than the 15G. It should be easier to pump the liquid through it due to less resistance meaning greater flow rate meaning better temperature control meaning better sugar extraction.

Right?

Stepping up to a 30G or above would be unreasonable, I'm sure.

Is there a down side to doing a mash in an over sized kettle?

Is there some minimum grain bed thickness dimension?

 

[bajaedition]

I'm trying to figure out where the reasonable dividing line is in terms of kettle sizes to be able to do experimental brews of 5G of beer (>5G of mash) and also to get the largest kettles to maximize the upper potential.

Moving liquid through the grain bed efficiently is the goal. It seem logical to me that the more surface area the better (within reason) for a given quantity of mash.

For example, take a 15G and a 20G standard kettle filled with a typical grist to water ratio for an average 5G of consumable beer. This is using the kettles at their minimum reasonable capacity. Admittedly, 15G is already too large for this.

The mash will be much shallower in the 20G than the 15G. It should be easier to pump the liquid through it due to less resistance meaning greater flow rate meaning better temperature control meaning better sugar extraction.

Right?

Stepping up to a 30G or above would be unreasonable, I'm sure.

Is there a down side to doing a mash in an over sized kettle?

Is there some minimum grain bed thickness dimension?

down size is filtering capacity and tendency to channel
most guys doing a 5 gallon batch size use 8 or 10 gallon mash tuns and hot liquor tanks depending on what they want the upper limit to be.

I use 8 and if I want a super high gravity beer, I do the Scotch Ale double mash technique which provides a 5 gallon heavy and a 5 gallon light.

98 percent of my beers are in the 1.040 to 1.065 range so 8 is very comfortable